1. Field of the Invention
A brake actuator arrangement includes a spring brake assembly utilizing a diaphragm with a central aperture and a push rod that goes through the aperture. The arrangement has a particular non-threaded securing device holding a central part of the diaphragm on the push rod.
2. Description of Related Art
A return spring is conventionally used in an air brake actuation device to bias an adapter push rod assembly into a nesting feature on a parking diaphragm while the parking side of the actuator is pressurized. Such an arrangement is intended to reduce negative effects of vibration on a center seal. The force of a return spring must be overcome during parking; this characteristic essentially equates to internal losses of the unit. The power spring, accordingly, must be large to overcome this return spring force and allow for adequate parking.
In a brochure titled Haldex LIFE SEAL Actuators Deliver Reliability, Long Life and Value (L20438; Rev. 2/08), a center-hole parking diaphragm held together with a threaded member is described. Seals are provided on a sleeve that runs the length of the threaded member.
U.S. Pat. No. 3,175,473 to Boteler et al. shows a spring brake assembly with a push rod passing through two plates and an apertured diaphragm. A retaining nut is fastened at the top of the push rod to hold the plates and diaphragm against a shoulder of the push rod. The entire assembly moves together with the push rod.
U.S. Pat. No. 5,507,217 to Plantan concerns an arrangement utilizing both a center-hole parking diaphragm held together by a threaded member and radial sealing on the outer diameter of a shaft. The aperture includes sealing beads, and a bolt goes through the aperture into the push rod so that the diaphragm moves with the push rod. Two plates generally provide radial sealing around the diaphragm aperture.
U.S. Pat. No. 6,164,187 to Stojic shows an apertured diaphragm sealed with a multi-fingered sealing clip on the opposite side of a plate from a power spring.
U.S. Pat. No. 2,578,730 to Nicholson et al. relates to a fluid pressure seal with two diaphragms held between plates. A fastening device is threaded through the two diaphragms into the plates to hold the diaphragms in place.
U.S. Pat. No. 3,020,094 to Murty et al. shows a diaphragm on a power spring side sealed by a separate clamp along its outer edges.
U.S. Pat. No. 3,101,219 to Herrera shows two screws holding a diaphragm against a service brake plate.
U.S. Pat. No. 3,244,079 to Herrera discloses an apertured diaphragm held against a plate by screws, thereby avoiding bulging.
U.S. Pat. No. 3,581,627 to Campanini shows an apertured diaphragm, which is sealed around a push rod by way of a screw.
U.S. Pat. No. 3,656,410 to Trower concerns a distributor actuator with an apertured diaphragm. The diaphragm is held against a plate and a rod by a cup-shaped member.
U.S. Pat. No. 3,696,711 to Berg et al. shows a massive annular diaphragm for creating a movable wall between service and spring brake portions.
U.S. Pat. No. 5,105,727 to Bowyer shows an apertured diaphragm with a boss. The diaphragm is held between a pressure plate and a hollow member.
U.S. Pat. No. 5,345,858 to Pierce and U.S. Pat. No. 5,640,893 to Stojic show hollow actuator rods through spring brake portions against which apertured diaphragms are sealed.
U.S. Pat. No. 5,377,579 to Pierce shows a diaphragm sealed between a funnel-shaped pressure plate and a hollow rod.
U.S. Pat. No. 5,937,733 to Stojic shows a diaphragm with an aperture sealed by a pressure plate forming a frustoconical surface around the diaphragm and a rod.
U.S. Pat. No. 6,360,649 to Plantan discloses a diaphragm sealed around the outside edge of a power plate.
Finally, U.S. Patent application publication 2007/0034465 to Thompson et al. discloses a flexible bushing assembly for the center seal of a spring brake push rod.
Unless manufacturers are driven to reduce weight or dramatically improve durability, current methods of using heavier designs with shorter useful lives are generally deemed adequate. The present invention addresses such weight and durability issues. While the references noted generally discuss uses of apertured diaphragms in spring brake assemblies and methods of sealing diaphragms, there is no suggestion of a multi-fingered sealing device to seal a diaphragm axially.